Buffers & buffer springs

The following are recommended guidelines for different pistol calibers AR-15 builds.

9mm
In our UDP-9 firearms we recommend using either a 5.4oz 9mm buffer kit which includes a standard length 5.4oz 9mm buffer, AR-15 carbine length buffer spring and buffer spacer OR a 6.3oz 9mm stainless steel buffer kit which includes a extended length 6.3oz stainless steel buffer and polished stainless steel carbine spring. If you are shooting suppressed or using hotter ammunition you can try using an 8oz or 10oz buffer with no spacer.

.40 S&W
We recommend using a 10oz extra heavy 9mm buffer kit which includes an extended length buffer and AR-15 carbine length buffer spring.

.45 ACP
We recommend using at least a heavy buffer kit which includes an 8oz extended length buffer and AR-15 carbine length buffer spring. If you are shooting suppressed or using hotter ammunition you can try using our 10oz buffer kit.

Buffer spring recommendations
We always recommend using a standard AR-15 carbine length buffer spring. Heavier springs can throw off the timing of the bolt hold open and are generally not needed.

**Please note using too heavy of a buffer or too powerful of a spring may cause the last round bolt hold open to become inoperable.


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